Pathogenic mechanisms underlying X-linked Charcot-Marie-Tooth neuropathy (CMTX6) in patients with a pyruvate dehydrogenase kinase 3 mutation

Perez-Siles, Gonzalo; Ly, Carolyn; Grant, Adrienne J.; Drew, Alexander P.; Yiu, Eppie M; Ryan, Monique M.; Chuang, David T.; Tso, Shih Chia; Nicholson, Garth A.; Kennerson, Marina

doi:10.1016/j.nbd.2016.07.001

Cited by 12 publications

(19 citation statements)

References 54 publications

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“…Our data shows the PDK3 mutation causes changes in the morphological features and distribution of the mitochondria in the patient-derived motor neurons, in line with our previous investigations using CMTX6 fibroblasts 6 . Our experiments showing the increased proportion of smaller mitochondria in the CMTX6 motor neurons ( Fig.…”

Section: Discussionsupporting

confidence: 92%

“…Our previous investigation using patient fibroblasts from the family initially describing the CMTX6 mutation, showed that increased kinase activity of the mutant PDK3 3 led to hyperphosphorylation of the E1 subunit of the PDC and consequently attenuation of the complex activity 6 . The report of a second unrelated family with the same genetic mutation, demonstrated the p.R158H as a mutational "hotspot" in the PDK3 gene 4 .…”

Section: Discussionmentioning

confidence: 99%

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Energy metabolism and mitochondrial defects in X-linked Charcot-Marie-Tooth (CMTX6) iPSC-derived motor neurons with the p.R158H PDK3 mutation

Perez-Siles

Cutrupi

Ellis

et al. 2020

Sci Rep

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PDK3 negatively regulates the pyruvate dehydrogenase complex (PDC) activity in the mitochondria by reversible phosphorylation of its first catalytic component (E1). PDK3 hence has a fundamental role in linking glycolysis to the energy producing Krebs cycle. The discovery of PDK3 has added to the growing list of CMT genes related to mitochondrial biology 5 , suggesting mitochondrial pathway deficits may be a common theme in some CMT neuropathies. Our previous investigations showed the p.R158H mutation produces a PDK3 enzyme with increased kinase activity 3. Experiments using CMTX6 patient fibroblasts demonstrated mutant PDK3 hyperactivity leads to increased phosphorylation of the PDC E1 subunit at specific serine residues and hence attenuation of the pyruvate dehydrogenase activity. Consequently, CMTX6 patient fibroblasts show increased lactate, decreased ATP and alteration of the mitochondrial network. Importantly, E1 hyperphosphorylation was reversed by treating the patient fibroblasts with a pan PDK inhibitor, dichloroacetic acid (DCA), opening a venue for therapeutic intervention for CMTX6 6. Despite the active research for therapies that can stop or ameliorate degeneration of axons, there is yet no cure for CMT. This fact can be explained in part by a reliance on animal models, transformed cell lines and heterologous recombinant systems for drug discovery 7. The use of human induced pluripotent stem cell (iPSC) technology has recently opened up the possibility to produce disease-relevant human models for drug discovery for inherited diseases in general and neurodegenerative disorders in particular 8. iPSC lines from CMT patients have increasingly been generated 9-11 and key pathological features for the disease have been replicated in some instances 12-15 in CMT patient derived motor neurons. In this study we have used patient fibroblasts from a recently identified family carrying the p.R158H PDK3 mutation 4 and, following confirmation of the E1 hyperphosphorylation as a CMTX6 disease signature, generated iPSCs from this patient. To eliminate the influence of variable genetic backgrounds from genetically unrelated controls, we also generated an isogenic wild type iPSC line by targeted gene correction using the CRISPR/Cas9 system. Our results show the E1 hyperphosphorylation is maintained in the CMTX6-derived iPSCs following reprograming of the patient fibroblasts and is also observed after differentiation into spinal cord motor neurons. Our data reveals abnormalities in the bioenergetic profile and mitochondrial morphological features in the CMTX6-derived motor neurons. Additionally, analyses of the organelle trafficking demonstrated the PDK3 mutation specifically affects mitochondrial trafficking in the patient motor neurons. Importantly, we have reversed the CMTX6 cellular phenotype both pharmacologically, using a pan PDK inhibitor, and by genetically correcting the p.R158H PDK3 mutation. Material and Methods Research guidelines and regulations. All research and cell culture procedures were conducted follow...

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Energy metabolism and mitochondrial defects in X-linked Charcot-Marie-Tooth (CMTX6) iPSC-derived motor neurons with the p.R158H PDK3 mutation

Perez-Siles

Cutrupi

Ellis

et al. 2020

Sci Rep

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“…38 IP 3 R3 defects may decrease mitochondrial Ca 2+ and predispose to defective bioenergetic or ER membrane function, which have been found in other forms of CMT. 39,40 In conclusion, our results provide further evidence that ITPR3 is a disease gene for CMT. Additional studies, ideally in neuronal or animal models, will be needed to elucidate the effects of the disease variants on IP 3 R3 function and evaluate the potential of targeting Ca 2+ flux as a therapeutic target in CMT.…”

supporting

confidence: 70%

Dominant mutations in ITPR3 cause Charcot‐Marie‐Tooth disease

Rönkkö

Molchanova

Revah‐Politi

et al. 2020

Ann Clin Transl Neurol

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Objective: ITPR3, encoding inositol 1,4,5-trisphosphate receptor type 3, was previously reported as a potential candidate disease gene for Charcot-Marie-Tooth neuropathy. Here, we present genetic and functional evidence that ITPR3 is a Charcot-Marie-Tooth disease gene. Methods: Whole-exome sequencing of four affected individuals in an autosomal dominant family and one individual who was the only affected individual in his family was used to identify diseasecausing variants. Skin fibroblasts from two individuals of the autosomal dominant family were analyzed functionally by western blotting, quantitative reverse transcription PCR, and Ca 2+ imaging. Results: Affected individuals in the autosomal dominant family had onset of symmetrical neuropathy with demyelinating and secondary axonal features at around age 30, showing signs of gradual progression with severe distal leg weakness and hand involvement in the proband at age 64. Exome sequencing identified a heterozygous ITPR3 p.Val615-Met variant segregating with the disease. The individual who was the only affected in his family had disease onset at age 4 with demyelinating neuropathy. His condition was progressive, leading to severe muscle atrophy below knees and atrophy of proximal leg and hand muscles by age 16. Trio exome sequencing identified a de novo ITPR3 variant p.Arg2524Cys. Altered Ca 2+-transients in p.Val615Met patient fibroblasts suggested that the variant has a dominant-negative effect on inositol 1,4,5-trisphosphate receptor type 3 function. Interpretation: Together with two previously identified variants, our report adds further evidence that ITPR3 is a disease-causing gene for CMT and indicates altered Ca 2+ homeostasis in disease pathogenesis.

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“…Similarly, PDC deficiency in a fetus causes congenital lactic acidosis and malfunctioning of the central nervous system, which can be rescued by a ketogenic dietary formula composed of high fat, adequate protein, and low carbohydrate [ 53 ]. Several identified mutants in human PDC have been inherited in peripheral neuropathy and in severe encephalopathy, characterized by increased lactate production, decreased oxidative phosphorylation, and defective mitochondrial homeostasis [ 54 55 ]. A clinical study based on serum amino acid metabolite profiling demonstrates that metabolic dysfunction in myalgic encephalopathy/chronic fatigue syndrome is linked to defects in PDC activity, resulting in excessive lactate secretion, while the increased mitochondrial respiration utilizes the amino acids [ 56 ].…”

Section: Regulation Of Pdc In Different Organsmentioning

confidence: 99%

Role of the Pyruvate Dehydrogenase Complex in Metabolic Remodeling: Differential Pyruvate Dehydrogenase Complex Functions in Metabolism

et al. 2018

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Mitochondrial dysfunction is a hallmark of metabolic diseases such as obesity, type 2 diabetes mellitus, neurodegenerative diseases, and cancers. Dysfunction occurs in part because of altered regulation of the mitochondrial pyruvate dehydrogenase complex (PDC), which acts as a central metabolic node that mediates pyruvate oxidation after glycolysis and fuels the Krebs cycle to meet energy demands. Fine-tuning of PDC activity has been mainly attributed to post-translational modifications of its subunits, including the extensively studied phosphorylation and de-phosphorylation of the E1α subunit of pyruvate dehydrogenase (PDH), modulated by kinases (pyruvate dehydrogenase kinase [PDK] 1-4) and phosphatases (pyruvate dehydrogenase phosphatase [PDP] 1-2), respectively. In addition to phosphorylation, other covalent modifications, including acetylation and succinylation, and changes in metabolite levels via metabolic pathways linked to utilization of glucose, fatty acids, and amino acids, have been identified. In this review, we will summarize the roles of PDC in diverse tissues and how regulation of its activity is affected in various metabolic disorders.

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Pathogenic mechanisms underlying X-linked Charcot-Marie-Tooth neuropathy (CMTX6) in patients with a pyruvate dehydrogenase kinase 3 mutation

Cited by 12 publications

References 54 publications

Energy metabolism and mitochondrial defects in X-linked Charcot-Marie-Tooth (CMTX6) iPSC-derived motor neurons with the p.R158H PDK3 mutation

Energy metabolism and mitochondrial defects in X-linked Charcot-Marie-Tooth (CMTX6) iPSC-derived motor neurons with the p.R158H PDK3 mutation

Dominant mutations in ITPR3 cause Charcot‐Marie‐Tooth disease

Role of the Pyruvate Dehydrogenase Complex in Metabolic Remodeling: Differential Pyruvate Dehydrogenase Complex Functions in Metabolism

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